[BUG] The segfault issue occurs when the smc_run command is used to test the MySQL database

[zhengchaoshao]

When I was using smc_run to test mysql on x86 or arm64, the segfault issue occurred.
Use the gdb to parse the core file. The information is as follows:
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00007f3cf0bd6374 in socket (domain=43, type=1, protocol=0) at smc-preload.c:117
#2 0x00007f3cf058b05d in ?? () from /usr/lib64/mysql/libmysqlclient.so.21
#3 0x00007f3cf0586249 in mysql_real_connect () from /usr/lib64/mysql/libmysqlclient.so.21
#4 0x000000000041ac9c in mysql_drv_real_connect (db_mysql_con=db_mysql_con@entry=0x7f3cc8000e40) at drv_mysql.c:351
#5 0x000000000041c24c in mysql_drv_connect (sb_conn=0x7f3cc8000db0) at drv_mysql.c:435
#6 mysql_drv_connect (sb_conn=0x7f3cc8000db0) at drv_mysql.c:370
#7 0x000000000040e781 in db_connection_create (drv=0x4a85c0 <mysql_driver>) at db_driver.c:329
#8 0x000000000043b956 in lj_vm_ffi_call ()
#9 0x000000000045d09c in lj_ccall_func ()
#10 0x00000000004379bd in lj_cf_ffi_meta___call ()
#11 0x00000000004399b7 in lj_BC_FUNCC ()
#12 0x0000000000427b0c in lua_pcall ()
#13 0x0000000000414bdf in sb_lua_op_thread_init (thread_id=4) at sb_lua.c:461
#14 0x000000000040c411 in worker_thread (arg=) at sysbench.c:809
#15 0x00007f3cefe1b22a in ?? () from /usr/lib64/libc.so.6
#16 0x00007f3cefe9dcf0 in ?? () from /usr/lib64/libc.so.6

The function pointed to by orig_socket is NULL.
The analysis is as follows:
CPUA CPUB
socket
initialize
dl_handle = dlopen(...
socket //dl_handle!=NULL
rc = (*orig_socket)(... //orig_socket is NULL，cause segfault

I think this issue occurs when users create sockets in multiple threads.
I'm not very familiar with smc-tool, and ask for help here.

I tried the following modifications to work around this problem, but it didn't solve the problem.
diff --git a/smc-preload.c b/smc-preload.c
index ee0ac83..83c5d80 100644
--- a/smc-preload.c
+++ b/smc-preload.c
@@ -96,6 +96,7 @@ static void set_bufsize(int socket, int opt, const char *envname) {
int socket(int domain, int type, int protocol)
{
int rc;

• int cnt = 0;

  if (!dl_handle)
  initialize();
  @@ -114,6 +115,16 @@ int socket(int domain, int type, int protocol)
  domain = AF_SMC;
  }

• while (orig_socket == NULL && cnt < 10) {

•   usleep(10000);
  

•   cnt++;
  

• }

• if (orig_socket == NULL) {

•   printf("Failed to create socket, orig_socket is NULL\n");
  

•   return -1;
  

• }

• rc = (*orig_socket)(domain, type, protocol);
  if (rc != -1) {
  set_bufsize(rc, SO_SNDBUF, "SMC_SNDBUF");

[GuangguanWang]

#7
This PR may help resolving the issue.